The origin may be, oh surprise, Israel. Engineers reportedly found the word "Myrtus" inside the virus, which could be an allusion to the Book of Esther. In the Old Testament, a Jewish woman called Esther marries Ahasuerus, King of Persia, the Iran of antiquity. The King's prime minister, Haman, doesn't like Esther and her cousin, Mordechai, so makes a plan to kill all the Jews in the Persian empire. Mordechai discovers the plan, and Esther tells the king who, enraged, orders Haman to be impaled and gives permission to the Jews to defend themselves against the attack. In the book, the Jewish kill Haman's sons and seventy-five thousand Persians.

Back in the real world, the Stuxnet virus didn't kill anyone or caused any fatal damage to Iran's nuclear plant. Designed to attack Siemens' Simatic S-7 controllers—used in nuclear power plants as well as oil pipelines and electrical power grids—the worm has been found in China, India, and Indonesia, but it has been especially virulent in Iran.

According to experts consulted by the New York Times, the secret code may not be a sloppy or whimsical reference from its developers, but a tool of psychological war. In recent years, Iran has been feeling the heat in their nuclear program, with scientists defecting and their secrets being compromised. The signature may just be a way of telling them "make no mistake, we are onto you." [NYT]